Why is nothing simple, feeling a bit deflated about the car now.

[signum_rob]

After learning the exhaust flexi was broken i got the new part and set about fitting, up on the ramps, tray off, loosed front 3 bolts which were a breeze, then the 2 clamp bolts holding to gearbox, then attacked the 3 bolts on the dpf flanges. I knew these were going to be absolute and utter ball ache and nothing has been more true. I thought the top was going to be hardest down to access but that came out not too bad, but the lower 2 just rounded as i expected. Seeing as i dont have any turbo sockets i couldnt use them and these bolts have welded themselves in so tight i dont think they would budge without sheering. Im guessing these are in such bad condition due to having the most road salt/water abuse. So i thought the only action was to grind off the rounded nuts, drill out the studs and replace with new bolts/nuts with anti shatter washers. But this is where ive hit a massive wall, none of my drill bits will do the job. Ive managed to drill through the core of one with a 4mm drill bit and assumed the best action with steel is to open hole gradually but it seems not. Soon as i go to next step of a 6/7mm drill bit it just kills the bit, i can only assume i dont have the right bits but the ones im using are hs bits which i thought were for hard metal. I have reached that stage where im close to launching a hammer through the windscreen. Can someone offer some words of wisdom before i hang from the ceiling. Any input greatly welcome.

[Edit100T]

Well I know from experience there's drill bits and then there's drill bits, go and buy a good quality set.
always gave things like that a long soak in penetrating oil then heated the bolts up with a blow torch and most come straight out, if they sheered then out came the drill/angle grinder, I don't have much patience so if the above failed it would be the sledge hammer and no I'm not joking : )

[patch22]

Earned my living in the engineering trade finished now pleased to say,came across similar situations on a regular basis,cobalt drill bits will do the job,but the key word is patience,these bits are very hard but very brittle have broke a few by rushing,don't know how much they run at but I should imagine they would be a bit pricey

[byebyeitsagsi]

Would have been much easier and probably cheaper to get an exhause fabricator to cut the old flexi out and weld a new one in its place.

[signum_rob]

Does anyone know the differences between carbide and cobalt tipped drill bits? Thanks

[patch22]

Does anyone know the differences between carbide and cobalt tipped drill bits? Thanks

Cobalt bits are for hard metal and carbide is for drilling predominantly ceramic material such as bathroom tile or masonry/brickwork etc.as i understand it anyway,but if it's wrong there'll be someone who'll know for sure

[signum_rob]

Thanks patch, have had a bit more of a scout on tinternet and it looks like i need colbalt bits with cutting paste at slow speed, none of which i used on the first run. You live and learn.

[Journeyman]

Thanks patch, have had a bit more of a scout on tinternet and it looks like i need colbalt bits with cutting paste at slow speed, none of which i used on the first run. You live and learn.

I had the same problem with one of the lower bolts when I changed the flexi pipe. Burnt out three cheap drill bits - as Patch says get a cobalt bit and take your time - you'll do it Rob. Then easy to reassemble and you'll be back to a quiet car and no fumes in the cabin. Good luck with it.

[tallaghtandy]

Get some cutting compound (trefolex) to use with the drill bit, will make a huge difference, most welding or engineering suppliers will stock it.